Emulated LANs

1
Emulated LANs

• With a few VLAN concepts added for spice

2
Problems

• Emulating a broadcast media LAN on a
  point-to-point WAN
• ARP?
• Multicast
• High Bandwidth Requirements

3
Typical Usage
4
Layers
Higher-layer
Higher-layer
protocols
protocols
(IP, ARP,
.
.
.)
(IP, ARP,
.
.
.)
Ethernet-like
interface
Signalling
Signalling
LANE
LANE
AAL5
AAL5
ATM
ATM
ATM
PHY
PHY
PHY
PHY
Host
Switch
Host
5
Setup

• Lan Emulation Client (LEC) contacts the Lan
  Emulation Configuration Server (LECS) to find out
  the ATM addresses of the Lan Emulation Server
  (LES) and Broadcast and Unknown Server (BUS) for
  the emulated LAN
• The LEC then registers with the LES and BUS
• The LES and BUS create virtual circuits to the LEC

6
Forwarding

• H1 LANE layer receives a packet for H2
• Since H2 is not in our cache, we send query to
  LES for H2 ATM address
• Since the query and VC setup may take seconds, we
  start sending data through the BUS
• We may wait until we receive several packets
  before setting up a separate virtual circuit
• The LES replies with the ATM address of H2
• H1 sets up a direct VC to H2 and adds an entry in
  the cache for H2

7
Other issues

• You can set up many ELANs with a separate LES and
  BUS for each ELAN
• A single ATM entity can be part of more than one
  ELAN

8
Multiple ELANs
Broadcast Domain 1
Broadcast Domain 2
H1
H3
H2
H2 cannot see H3
9
What About VLANs?

• VLANs create virtual broadcast domains out of
  whatever physical networks that are available
• Most Ethernet switches will allow for VLANs to be
  created from a subset of the ports on the switch.
• Machines that are not in this subset can not
  access the VLAN machines
• The VLAN can extend across the internet

10
Big Picture
H5
H4
Ethernet links
ATM links
H3
H6
E2
E1
Ethernet switch
H7
H12
H9
Ethernet links
H13
H10
E3
E4
Ethernet switch
H11
ATM switch
ATM-attached
host
11
IEEE 802 Model

• Physical (PHY)
• Medium access control (MAC)
• Logical Link Control (LLC)
• Higher level services (HLS)

12
802.1 MAC Bridge Design Space

• MAC Layer defines interface to a Port
• Relay/Forwarding defines behavior of received
  packet as sent to other ports
• Broadcast behavior
• Unicast behavior
• Multicast behavior
• Trunking behavior

13
802.1 MAC Bridge Model
End Node
End Node
LLC
LLC
Bridge
Relay
MAC
MAC
MAC
MAC
PHY
PHY
PHY
PHY
14
802.1 LAN Switch MAC Bridge
End Node
LLC
End Node
LLC
MAC
MAC
PHY
PHY
15
802.1 MAC Bridge Model ATM ELAN
End Node
End Node
Bridge
Relay
ATM Switch
ATM Switch
16
802.1 MAC Bridge Model ATM ELAN
End Node
End Node
Bridge
LLC
Relay
MAC
MAC
PHY
PHY
ATM Switch
17
Router Components
18
Architecture
LES
Mac
Mac
Mac
Mac
Ethernet
BUS
Relay
ATM Switch
Mac
LEC
ATM
Plug and Play
19
Architecture
Mac
Mac
Mac
Mac
Ethernet
LEC
Relay
LES
PVC
BUS
ATM Switch
Mac
ATM
20
Architecture
POS
Mac
Mac
Mac
Mac
Ethernet
Relay
Relay
Ether Switch
Mac
POS
21
VPN
Mac
Mac
Mac
Ethernet
Relay
Mac
VPN
Translate IP address to TCP connection
Send to TCP connection
22
VPN
128.187.23.44
96.55.77.88
Host1
Host2
Set up TCP connection, get local
address96.55.77.67 This looks like a P-P link
96.55.77.1
VPN Server